The present invention generally relates to syringes, including small volume (e.g., about 1 cc or less) retractable safety syringes.
In recent years, the public (e.g., medical personnel and healthcare providers, drug addicts, drug users, and the like) has become increasingly aware of the health hazards associated with needle reuse and accidental needle prickings. For example, at least twenty blood-borne pathogens may be transmitted by the reuse of needles or accidental needle prickings. For example, these blood borne pathogens may include and are not limited to Human Immunodeficiency Virus (HIV), Acquired Immunodeficiency Syndrome (AIDS), Hepatitis B, Hepatitis C, syphilis, malaria, tuberculosis, and herpes. Despite the awareness of the risk of needle reuse and accidental needle prickings, at least 36 percent of HIV/AIDS cases and more than 50 percent of Hepatitis B and Hepatitis C cases in the United States may be linked to the sharing of needles among drug addicts. Accordingly, there is a need to curb the practice of sharing needles among drug addicts.
The problem of needle sharing or needle reuses is further amplified when viewed in relation to the world population. For example, approximately 30 percent of reported HIV/AIDS cases in Brazil, Chile, Uruguay, Paraguay and Argentina are directly related to the sharing of contaminated needles among drug addicts. Approximately 70 percent of the HIV cases reported in China are directly linked to the sharing of contaminated needles. In eastern European countries, 80 percent of injection drug addicts admit to sharing contaminated needles. Approximately 43 percent of HIV/AIDS cases reported in Poland and Yugoslavia are linked to the sharing of contaminated needles among drug addicts.
Accidental needle prickings also pose a threat to healthcare workers. In particular, approximately one million accidental needle prickings are reported by healthcare workers annually. However, it is believed that at least three million accidental needle prickings occur each year, of which about two million are unreported. Various studies estimate that out of all the accidental needle pricking injuries that occur to nurses, approximately 40 percent to 53 percent go unreported. Various studies also estimate that out of all the needle pricking injuries that occur to laboratory technicians, approximately 92 percent go unreported. Various studies further estimate that out of all the needle pricking injuries that occur to physicians, approximately 70 percent to 95 percent go unreported.
In 1997, the Center for Disease Control and Prevention (CDC) sponsored a study that found that approximately 76 percent of needle pricking injuries could be avoided by using safety needles. Presently, there are at least 250 types of safety syringes. Unfortunately, the retractable safety syringes that currently exist have been criticized for various problems associated in operating the retractable safety syringe and its ineffectiveness.
One type of safety syringe is a vacuum assisted safety syringe wherein the needle of the syringe is retracted into a syringe body after a piston engages a needle holder due to a retraction force of a variable vacuum compartment. The retraction force of the variable vacuum compartment is a function of the surface area of the piston as it is traversed from a retracted position to an engaged position. If the variable vacuum compartment is not sufficiently large, then the retraction force of the variable vacuum compartment may not be sufficient to withdraw the needle holder and needle into the syringe body. This problem is particularly pronounced when the retractable safety syringe has a small variable fluid chamber of about 1 cc or less. Small variable fluid chambers require a syringe body having a small diameter. Correspondingly, the variable vacuum compartment is also small limiting its maximum potential retraction force. If the retraction force of the variable vacuum compartment is not greater than a force required to traverse the needle holder and needle into the retractable safety syringe, then the needle will still be exposed outside of the syringe body thereby possibly pricking a medical professional or allowing a drug addict to reuse the needle.
Accordingly, there is a need in the art for an improved safety syringe.